Water-cooled server farms produce waste heat in the range of MW as hot water at a substantially constant temperature level of about 80° C. The hot water can be used for heating purposes or as service water for industrial or domestic use. However, while a demand for hot water generally fluctuates strongly during the day, the supply of hot water from a server farm remains constant, making such a use of waste heat inefficient.
Converting the thermal energy of the waste heat in mechanical energy, e.g. by driving a steam turbine, requires high temperatures of several hundred degrees Celsius.
It is well known in the art to use waste heat for generation of electric energy. For instance, RU 2 379 820 C1 describes a thermoelectric converter employing a permalloy composition having a Curie temperature Tc of e.g. 70° C. Above the Curie temperature, permalloy is paramagnetic, below the Curie temperature, permalloy is ferromagnetic. In a closed magnetic circuit an excitation coil is arranged which is supplied by a DC source. Inside the coil permalloy is arranged for altering the magnetic flux in the coil by heating and cooling the permalloy above and above the Curie temperature.